This application in general relates to an apparatus for preparation of a blood sample which dispenses measured amounts of a blood sample and a diluent into a reaction tube which contains a predispensed reagent.
Sample preparation systems are known in the prior art, and may include needles which pierce a closure on a sample tube to provide communication between blood in the sample tube and the system.
In general, complicated valving systems have been utilized to withdraw an amount of a blood sample from a closed blood sample tube, and move that blood sample to a reaction tube. Many prior art systems use a diluent as a means of assisting the movement of the blood sample through the system. In the complicated prior art systems, the amount of diluent required has been undesirably large. Thus, the blood reaching the reaction tube is overly diluted and reactions within the reaction tube require an undesirably long period of time.
It is known in the prior art to aspirate blood from the sample tube through the needle, and to a reaction tube by connecting the needle to a source of suction such as a pump. In one such prior art system disclosed in the U.S. Pat. No. 4,811,611, the aspiration system which is used to withdraw blood from the tube through the needle initially contains a charge of air. As the needle punctures the closure in the tube, this charge of air communicates with the tube, relieving a vacuum in the tube. A problem with the use of such prior art systems is that a fixed charge of air is typically utilized. In so-called "short draw" sample tubes wherein there is an unusually small amount of blood, there may be a greater vacuum in the sample tube. In such cases, the charge of air in the prior art system may be insufficient to fully relieve the vacuum. Further, the use of the aspiration system to relieve vacuum in the tube results in a complex aspiration system including a number of valves. It would be desirable to reduce the complexity of the aspiration system.
In addition, in the prior art system disclosed in the above referenced patent the valving between the sample tube, the reaction tube, and the diluent pump is somewhat complicated. It would be desirable to reduce the complexity of the valving for the various systems.
Also, the known systems for rinsing or cleaning the needle after removing a sample from the sample tube is somewhat complicated and inefficient.
Finally, the prior art systems have typically used fixed reaction chambers.